Although conventional percutaneous, transluminal, coronary angioplasty (PTCA) and percutaneous, transluminal, angioplasty (PTA) procedures have been somewhat effective in treating coronary artery disease, incising devices, such as cutting balloons, are currently viewed by many as the next generation treatment option for the revascularization of both coronary and peripheral vessels. The cutting balloon mechanism is unique in that the balloon pressure is distributed over one or more blades (i.e. microtomes). The blade(s) function as stress concentrators and cut initiators in PTCA and PTA procedures. Importantly, PTCA and PTA procedures that employ cutting balloons for this purpose have been proven to minimize vessel recoil, lessen vessel injury and lower the rate of restenosis, as compared to conventional PTCA and PTA procedures.
In the past, typical cutting balloons have been prepared by first encapsulating a portion of an incising element, such as a metal cutting blade, in a blade pad. The blade pad is then adhesively bonded to the smooth outer surface of an inflatable balloon. In some instances, however, this type of bond between the blade pad and the balloon has been somewhat inadequate due to the inability of the adhesive to bond to the smooth surfaces of the balloon and pad. In particular, relatively long blades require a strong bond due to the differential expansion rate of the metal blade and the flexible balloon material. An inadequate bond is especially troublesome in light of the grave consequences that can result if a blade pad de-bonds from the balloon while the balloon is located in a sensitive area of the patient. For example, a de-bonding of a blade pad from an inflatable balloon in or near the heart would in most cases require immediate, high-risk open-heart surgery to remedy.
The cutting blades used in cutting balloons are extremely sharp (e.g. three to five times sharper than a conventional scalpel). In the absence of suitable precautions, the sharp blades can tear, cut or perforate the thin, fragile inflatable balloon during assembly of the cutting balloon, handling or during clinical use. In a worst case, a balloon perforation or tear can result in an unsuccessful PTCA/PTA procedure and the loss of inflation fluid into the patient's vasculature.
In a typical PTCA and PTA procedure, a cutting balloon is advanced through the vasculature of a patient with the balloon in a deflated configuration. The balloon is then precisely positioned across a lesion in the vessel that is to be treated. Once the balloon has been properly positioned, fluid is infused into the balloon to expand the balloon into an inflated configuration. As the balloon expands, the blades cut into the lesion and the surface of the balloon presses against the lesion, dilating the lesion to increase the effective diameter of the vessel. In turn, the portion of the lesion that is in contact with the balloon produces reactive forces on the balloon. For a lesion that is lubricious, the reactive forces may overcome the frictional forces between the balloon and the lesion. If this happens, slippage can occur between the balloon and the lesion resulting in unwanted movement of the balloon relative to the lesion. For instance, the reactive forces can cause the balloon to shoot forward or backward through the vessel in a longitudinal direction (i.e., “the watermelon seed effect”). This unwanted movement is often deleterious to the PTCA and PTA procedure because dilation and cutting may not occur at the desired location in the vessel. Thus, unless unwanted movement of the balloon relative to the lesion can be prevented, the effectiveness of the PTCA and PTA procedure may be significantly reduced.
In light of the above, it is an object of the present invention to provide cutting balloons and methods for their manufacture having cutting blades that are strongly bonded to the surface of an inflatable balloon. It is another object of the present invention to provide methods for forming surface textures on one or more cutting balloon surfaces to promote adhesion between the cutting blades and the inflatable balloon, to improve traction between the cutting balloon and the arterial wall, or to prevent inflatable balloon perforation by a cutting blade. Yet another object of the present invention is to provide cutting balloons and methods for their manufacture that are easy to use, relatively simple to implement, and comparatively cost effective.